Tap

What is a Tap?

A tap is a cutting tool used for creating threaded holes. Taps are used to make internal threads in workpieces, which are necessary, for example, for securing bolts and screws. Taps are made from various materials such as high-speed steel (HSS), powdered high-speed steel (HSCo), and carbide.

Types of Taps and Their Applications

There are two main types of taps: cutting taps and forming taps, also known as roll taps. Cutting taps remove material, while forming taps displace the material to form threads through pressure. Taps are also available for different thread types, such as through-hole and blind-hole threads. Through-holes typically use straight-flute taps, which push the chips through the hole. Blind-hole threads use spiral-fluted taps, which lift the chips out of the hole.

Using Taps in Machining

In machining, taps are an essential part of thread production. The process begins by drilling a pilot hole in the workpiece, the size of which is determined by the internal diameter of the thread. The size of the pilot hole is important—when using roll taps, it should be larger than with cutting taps. Lubrication, such as cutting fluid or tapping paste, is used during threading to reduce friction and heat.

Hand and Machine Taps

Cutting taps can also be used manually with a separate tap wrench. When tapping by hand, it's important to periodically reverse the tap to prevent chips from clogging and potentially breaking the tool. In contrast, roll taps are suitable only for use with CNC machines, where their accuracy and efficiency can be fully utilized.

Drilling Pilot Holes for Taps

In modern CNC machining, it's important to note that when drilling a pilot hole for threading with a carbide drill bit, the hole should be larger than when using a high-speed steel drill bit. This is due to the differences in hole accuracy produced by different types of drill bits. A hole drilled with a carbide bit may be tighter, so the pilot hole size must be adjusted accordingly.

Summary

The tap is a key tool in machining, used for producing threaded holes in various metal parts. Taps are available in a range of materials and for different applications, such as through-hole and blind-hole threads. Cutting taps are also suitable for hand use, while forming taps are used in CNC machining. The correct size of the pilot hole and proper lubrication are critical for successful threading. Using taps requires precision and an understanding of the requirements and characteristics of different tool types.